1. Field of the Invention
The present invention relates to a driving circuit for light emitting diodes, and particularly to a dimming technique for light emitting diodes used as a backlight for a liquid crystal panel.
2. Description of the Related Art
As a backlight for a liquid crystal panel, white light-emitting diodes (which will be referred to as “LEDs” hereafter) having improved properties from the perspective of a long operating life, low power consumption, and a wide color range are employed instead of conventional CCFLs (Cold Cathode Fluorescent Lamps) or EEFLs (External Electrode Fluorescent Lamps).
Each LED to be driven is provided to the back face of a liquid crystal panel. The increasing size of liquid crystal panels leads to a difficulty in driving all the LEDs using a single driving circuit. In order to solve such a problem, in general, the liquid crystal panel is divided into multiple areas, and driving circuits are provided in increments of areas.
[Patent Document No. 1]
Japanese Patent Application Laid Open No. 2004-32875
[Patent Document No. 2]
Japanese Patent Application Laid Open No. 2002-252971
[Patent Document No. 3]
Japanese Patent Application Laid Open No. 2007-028784
[Patent Document No. 4]
Japanese Patent Application Laid Open No. 2007-173813
Such an arrangement employing LEDs as a backlight is capable of providing an improved contrast ratio by changing the luminance of the backlight (area control operation) according to the contrast of an image to be displayed on the liquid crystal panel.